<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>

        .button {
            width: 100px;
            height: 30px;
            line-height: 30px;
            text-align: center;
            position: relative;
            border: none;
            outline:none;
            cursor: pointer;
            background-color: transparent;
        }
        .button::after, .button::before {
            content: "";
            position: absolute;
            width: 20%;
            height: 20%;
            border: 2px solid;
            transition: all 0.6s ease;
            border-radius: 2px;
        }
        .button::before {
            top: -2px;
            left: -2px;
            border-bottom-color: transparent;
            border-right-color: transparent;
            border-top-color: #566473;
            border-left-color: #566473;
        }
        .button::after {
            bottom: -2px;
            right: -2px;
            border-top-color: transparent;
            border-left-color: transparent;
            border-bottom-color: #566473;
            border-right-color: #566473;
        }

        .button:hover:after, .button:hover:before {
            width: 100%;
            height: 100%;
        }
    </style>
</head>
<body>
        <button class="button">返回</button>
</body>
</html>